The ability to attach living cells to surfaces has enabled the study of many key behaviors in biology, including immune synapse formation, stem cell differentiation, cancer cell motility, and drug response. In most of these studies, cells of interest are exposed to surfaces, such as slides or supported lipid bilayers, that have been patterned with biomolecules that engage cellular receptors in a well-defined way. Outside these experiments, immobilized biomolecule arrays have also shown promise in fundamental studies of biofuel production, the investigation of antibody-antigen interactions, and the construction of biofuel cells based on enzymes.
Although most of these studies have capitalized on interactions between the surface integrins of adherent mammalian cells with proteins bearing “RGD” peptide motifs, there is a need to develop an alternative strategy in which synthetic DNA strands introduced on the cell surfaces bind to sequence complements displayed on the binding surface. Demonstrated advantages of this approach include its generality for all biological cell types, exceptionally high efficiency, and ability to generate complex multicellular patterns through the use of multiple capture sequences. In addition, the DNA-based adhesion event has been shown to exhibit minimal changes in cellular behavior because it does not involve native cell receptors. In previous studies, this strategy was used to measure the metabolism of single cells, conduct single-cell RT-PCR analysis, study the diffusion of paracrine signaling molecules, and connect cells directly to AFM tips. The technique has also been applied to the formation of three-dimensional cell clusters in suspension.
This conjugation method, like most other approaches to cell capture, benefits greatly from the development of streamlined techniques that can generate small and elaborate patterns of DNA with high precision and high throughput. This is typically done through the use of traditional photolithography, soft lithography, Dip-Pen nanolithography, inkjet printing, and electron beam lithography. Although these methods have yielded impressive advances in the types of arrays that can be generated, few if any can successfully combine the ability to generate sub-micron feature sizes with biomolecular compatibility and high patterning speed. This latter feature is highly important for the future commercialization of these platforms for diagnostic use, for example.
Accordingly, a new strategy for the generation of complex patterns of DNA molecules on surfaces is needed.